Automatic thread cutting attachment for sewing machines



AUTOMATIC THREAD CUTTING ATTACHMENT FOR SEWING MACHINES Filed June 18, 959

Sept. 12, 1961 J. J. WANNER 2 Sheets-Sheet 1 INVENT OR. 3:1,? Wan/7C" Sept. 12, 1961 J. J. WANNER 2,999,473

AUTOMATIC THREAD CUTTING ATTACHMENT FOR SEWING MACHINES Filed June 18, 1959 2 Sheets-Sheet 2 INVENTOR. 3:5,, -7 Wanner 21, EM, .124. W

ite htates This invention relates to an automatic thread cutting attachment for sewing machines whereby the threads are closely and neatly cut from the fabric without injury thereto upon completion of the sewing operation.

Heretofore, threads have been out, following the sewing operation, by an operator with a hand cutter or a stationary cutter fixed to some part of the machine which required that a long length of thread be pulled from the machine supply in order to reach the stationary cutter thus involving wasted thread and in neither instance is the cutting one automatically upon completion of the sewing operation. Furthermore, in some instances where automatic thread cutting attachments have been employed, the feeding means often fed the fabric at a faster rate than it could be accommodated by the automatic thread cutting attachment thereby resulting in a pile-up of material between the needle and the feeding mechanism and the thread cutting attachment.

Accordingly, an object of the present invention is the provision of an improved automatic thread cutter for sewing machines which obviates the above mentioned diificulties.

Another object of the invention is in the provision of an automatic thread cutting attachment provided with means for automatically cutting the thread immediately upon completion of the sewing operation.

Another object of the invention is in the provision of an automatic thread cutting attachment for cutting the thread automatically upon completion of the sewing operation wherein the amount of thread wasted is minimized.

Still another object of the invention is in the provision of an improved automatic thread cutting attachment which can be added as an accessory to any conventional needle sewing machine without substantial reconstruction thereof in which the action of the cutter bars is synchronized with the feeding mechanism of the machine to avoid pile-up of fabric.

A stull further object of the invent-ion is an improved automatic thread cutter which is simple in construction and efficient in operation.

Other objects and advantages will be apparent to those skilled in the art from the following description taken in connection with the accompanying drawings in which:

FIG, 1 is an end view illustrating a sewing machine equipped with an automatic thread cutting attachment embodying the present invention.

FIG. 2 is an end view, looking in the same direction as FIG. 1, of the needle carrier and a portion of the driving means therefor.

FIG. 3 is an end view of the thread cutting attachment, looking in the same direction as FIG. 1.

FIG. 4 is an end view of the thread cutting attachment of FIG. 3 illustrating the position of the cutter bars in cutting relation and looking in the opposite direction to that of FIG. 3.

FIG. 5 is an end view of the thread cutting attachment of FIG. 4 showing the cutter bars in their open position.

Referring now to the drawings in which like numerals designate like parts, a conventional sewing machine 2 is shown provided with a work plate 3, a needle carrier 4, and a needle 5 mounted on the carrier. Also illustrated are presser foot 6, head 7, and a needle thread tensioning rod 9, all of the above elements being conventional atent Z,%9,473 Patented Sept. 12, 1961 parts of a conventional sewing machine to which my automatic thread cutting accessory 10, embodying the invention, is attached. Referring particularly to FIG. 2, needle carrier 4 is connected to rotating element 11 by means of a suitable connecting rod 12. Rotating element 11 is connected to and driven by the driving means for the sewing machine 2, said driving connection forming no part of the present invention and therefore is not shown. Needle carrier 4 is pivotally connected to the machine 2 by pivot pin '13 and thus receives limited rotary or oscillatory motion with respect to pivot pin 13 when driven by rotating element 11.

Similarly, feed dogs 14 are connected to the driving means for the machine 2, said driving connection forming no part of the present invention and therefore is not illustrated. When machine 2 is driven by its driving means, feed dogs 14 are given a slightly upward motion to engage the under side of the fabric or the work and are then caused to move in a horizontal direction from right to left in FIG. 1, and thereafter a slightly downward motion to disengage the fabric and move from left to right in FIG. 1 and then upward to again engage the fabric. As noted heretofore, feed dogs 14 and rotating element 11 are both driven by the same driving means, that supplied for machine 2.

Thread cutting accessory 10 comprises a lower bar 15 carrying an auxiliary bar 16 for detachably securing a cutter blade 17 by means of a clamp screw 18. Also carried by lower bar 15 is a curved fabric guard 19 for receiving work fabric and thread from feed dogs 14 and for urging such fabric and threads sidewardly with reference to lower bar 15 after passing cutter bar 17 to prevent fouling of the thread cutters by the work fabric or thread.

An upper bar 29 is pivotally connected to bar 15 by means of a pivot 21 and a screw 22. The hole 23 provided in upper bar 20 for receiving screw 22 is somewhat elongated along the longitudinal axis of upper bar 20 so that upper bar 20 may be adjusted relative to bar '15 and to provide some adjustment of the cutters and the biasing means. Upper bar 24] also carries an auxiliary bar 24 for detachably securing an upper cutter blade by means of a clamp screw 26. A spring 27 urges upper bar 20 toward lower bar 15 and may be adjustably secured by a screw 28 threadedly engaged with lower bar 15 and passing through a clearance hole 29 in upper bar 20, or, desired, screw 28 may be positively secured to bar 15.

As is best shown in FIGS. 4 and 5, a member 30 is pivotally connected to lower bar 15 by pivot pin 31. Roller 32 is carried by member 30 at one end thereof, the other end thereof having a sloping cam-like surface 33. A roller 34 is fitted to the needle carrier 4 with pivot pin 13 disposed between roller 34 and needle 5 so that when needle 5 is moving in a generally upward direction, roller 34 will be moving generally downward. Roller 34 is also disposed adjacent and in engagement with cam-like surface 33 and thus imparts limited rotary or oscillatory motion of member 30 with respect to its pivot pin 31 when driven by rotating element 11. Up per bar 20 is provided with a downwardly extending portion 35 having a lower surface 36 engaging the top of roller 32. Thus, upper bar 2% is caused to move in limited rotary or oscillatory motion with respect to pivot 21 when driven by rotating element 11.

The timing on sewing machines is such that feed dogs 14 advance the work fabric only when needle 5 is raised. In accordance with the present invention, and as noted heretofore, the movement of roller 34 is downward when the movement of needle 5 is upward. The downward movement of roller 34 against cam-like surface 33 causes roller 32 to be elevated and this in turn elevates upper bar and upper cutter bar during a feeding operation.

The force of spring 27 is not sufiicient to cause the cutters to cut through the fabric or cloth being fed through the machine. Also, upper cutter blade.- 25,. may carry a non-cutting portion disposed to contact the fabric and prevent the cutters from cutting it in the manner disclosed in a copending application of Ritchie F. Ball, Serial No. 680,065, filed August 26, 1957, now Patent 2,920,592, issued January 12, 1960, and assigned to applicant. However, upon completion of the sewing operation and the Work fabric having passed beyond the fabric guard and the cutters 17 and 25, spring 27 urges cutter blades 17 and 25 together with sutficient force to cut the thread.

Thus itwill be seen that the thread cutting attachment is automatic in operation, simple in construction and automatically cuts the thread upon completion of the sewing operation with a minimum amount of waste thread. It will also be seen that my improved thread cutting attachment correlates the action of the thread cutter with the work feeding mechanism so that the cutter bars are open during a feeding operation thereby avoiding pile-up of work fabric between the cutter blades and the feeding mechanism.

While a particular embodiment of the invention has been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention and I intend, therefore, in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.

Having thus described my invention, What I claim as new and useful and desire to secure by United States Letters Patent, is:

1. In a sewing machine comprising in combination, needle carrier means adapted for limited oscillatory movement, work feeding means, means for driving the needle carrier means and said feeding means, and automatic thread cutting means including a pair of members pivotally connected together, and each having a free end, complementary cutting blades detachably secured to the free end of each of said members, means biasing said cutting blades together into cutting relation, a floating member pivotally supported by one of said pair of members with a portion in engagement with the other member of said pair, and a fourth member connected to the needle carrier means and in engagement with another portion of said floating member at a location spaced from the point. of pivotal support thereof for causing said cutting blades to move out of cutting relation in synchronism with feeding movements of the work feeding means, and means carried by one of said members for preventing cutting action of said blades when a work piece is therebetween.

2. For use in a sewing machine having work feeding mechanismv and driving means, an automatic thread cutting attachment comprising a pair of members pivotally connected together and each having a free end, complementary cutting blades detachably secured to the free ends of said members, means biasing said cutting blades into cutting relation, and means including a third member pivotally supported by one of said pair of members with a portion of the third member in engagement with the other member of said pair and having a cam-like por tion at a location spaced from its point of pivotal support and adapted to be engaged in driving relation by said driving means for causing said cutting blades to move outof cutting relation in synchronism with feeding movements of the feeding mechanism, and means carried by one of said members for preventing cutting action of said blades when a work piece is therebetween.

References Cited in the file of this patent NITE STATES PATENTS 

